public class Test8 {
    public static void main(String[] args) {
        double r = 5.5;
        // Math.PI为Math类中提供的现成的数学中π的值
        double c = 2 * r * Math.PI;
        double s = r * r * Math.PI;
        System.out.println("半径为" + r + "的圆的周长为" + c + "，面积为" + s);
    }
}